In general, to manufacture a semiconductor integrated circuit, various processes such as film forming, etching, oxidation and diffusion are performed on a target object such as a semiconductor wafer in a semiconductor processing system. In this case, the production yield of a wafer where micro-processing is performed at a submicron level needs to be improved. For this, an atmosphere in a wafer transfer area of a processing apparatus, as well as in a clean room in which the processing apparatus (semiconductor manufacturing apparatus) is installed, is strictly managed. Therefore, fine particles or an organic gas in the atmosphere that may cause defects in products are removed (see, for example, Japanese Patent Application Publication Nos. 2002-75844 and 2002-151372).
To be specific, fine particles are usually removed by an ULPA (ultra low penetration air) filter. The organic gas is removed by an organic gas removal filter formed of a chemical filter such as activated carbon. For example, chemical filters or ULPA filters are disposed at a ceiling portion of the clean room that accommodates the processing apparatus, forming a downstream current of clean air. Further, the processing apparatus has a handling space for handling the wafer or a stocking space for storing the wafer at its front end portion to transport the wafer to a processing chamber. Chemical filters or ULPA filters are usually installed at a ceiling portion or a lateral side portion of the handling space or a stocking space to form a laminar flow of clean gas (e.g., air or N2 gas).
However, once reaching a specific adsorption amount of the ULPA filter or the organic gas removal filter, the collecting ability thereof decreases rapidly. Therefore, in order to keep the production yield high, it is necessary to find out the lifetime of the filter accurately.
Hereinafter, how to manage the lifetime of the organic gas removal filter, for example, will be described. First, the atmosphere that has passed through the organic gas removal filter in the clean room or the processing apparatus is made to go through an adsorptive material for organic gas for a specified amount of time or at a specified flow rate. Thus, organic gas having remained in the atmosphere are completely adsorbed and collected by the adsorptive material. The adsorptive material that has adsorbed the organic gas is then transferred to a measurement specialist. Then, the measuring specialist heats the adsorptive material to completely desorb the organic gas having been adsorbed thereto, and measures the concentration of the desorbed organic gas.
Thereafter, based on the measurement result obtained by the measuring specialist, it is determined whether the lifetime of the organic gas removal filter comes to an end. For example, if the organic gas concentration at the measuring point of time was higher than a reference value, it means that the organic gas is not sufficiently removed by the filter. That is, the lifetime of the filter is deemed to have expired. This also applies to a filter for removing an amine gas, which is a kind of organic gas.